[Android Pro] Android签名与认证详细分析之二(CERT.RSA剖析)

转载自: http://www.thinksaas.cn/group/topic/335449/

               http://blog.csdn.net/u010571535/article/details/8992543#

一、Android证书的格式

Android签名中证书的格式采用X.509标准的版本三,不过省略了一些内容。

X.509证书格式如下图所示:

二、证书的格式示例

从Chrome浏览器中导出一个证书,打开之后的样子如下图所示:

说明:由上图可以看出,在证书中,开发者的公钥是显式存在的。

三、对CERT.RSA进行详细解析

重要说明:编写Java程序和编写Android应用App解析Apk的CERT.RSA文件,得到的结果是不一样的。按道理,都是解析的同一个文件,为什么结果不一样呢?经过我们分析,发现不一样的地方是开发者公钥,但是这是由于二者的显示格式不同导致的。App解析得到的文件时十六进制显示的,而Java解析得到的结果却是十进制显示的。我们利用Java的BigInteger编写程序,将十六进制转换为十进制,验证了我们的猜想。

明确了上面的问题之后,对CERT.RSA 文件进行详细解析,得到下图:

说明:

(1)首先,我们的通常所说的证书的签名,是生成证书的时候CA对整个证书的所有域签名的得到的,而不是对某一部分签名得到的。整个签名就是上图中部分一的最下面的一段十六进制的内容;

(2)编程中的获取到的内容实质上是就是上图中的部分二,这是一个证书的所有内容;

(3)部分一种的公钥等信息就是从部分二中得来的,可以直接在部分二中找到。

(4)可以猜测,部分一中的其他信息也是从部分二中得来,只不过编码方式不一样,所以显示不同而已。

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可以通过: openssl pkcs7 -inform DER -in CERT.RSA -noout -print_certs -text  将 CERT.RSA证书中的内容答应出来。

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 1005375368 (0x3beccf88)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, O=Android, CN=Android Debug
        Validity
            Not Before: Dec 29 10:10:49 2014 GMT
            Not After : Dec 21 10:10:49 2044 GMT
        Subject: C=US, O=Android, CN=Android Debug
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    00:d8:b9:a8:66:5f:09:b0:04:86:3f:23:9e:c2:84:
                    93:a0:e3:dc:a2:5f:d3:ab:48:29:e9:e6:33:16:69:
                    56:87:4f:34:41:ce:be:3e:d0:a4:fa:33:27:e7:79:
                    7d:d3:0b:63:22:d3:27:f9:7b:f2:23:30:23:13:39:
                    24:4c:92:f2:15:60:35:ed:91:87:77:86:e7:f0:df:
                    2d:93:fd:59:26:86:93:4e:e5:13:e2:bf:55:5a:6a:
                    e7:3d:ac:48:50:10:d4:96:71:2d:c7:f9:df:91:0b:
                    b8:b0:0f:8d:b9:f2:8f:ec:65:33:c6:6c:a9:79:b1:
                    da:74:d1:0f:cc:7a:c3:ed:d1:a2:85:42:86:ae:88:
                    2a:dd:3c:8b:b0:d5:e5:45:07:42:a0:96:65:b4:ac:
                    2f:98:7e:8a:36:2f:b8:0d:a7:1c:0f:38:f1:56:9c:
                    13:f6:3c:a0:2c:f7:a9:e8:cb:17:95:44:4f:dc:e2:
                    ce:b7:9e:a3:f8:c2:fa:71:c0:f0:20:76:29:34:34:
                    d9:e0:18:12:f9:ec:40:a9:2a:f1:39:cd:30:43:da:
                    de:92:71:92:88:fd:28:0a:17:b7:cd:c8:d8:fb:45:
                    ca:1c:61:bc:13:91:2e:01:b2:20:36:1b:18:b8:aa:
                    e0:95:e0:ab:98:fa:9c:1b:6b:7f:bd:27:66:ab:5e:
                    d0:9b
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Subject Key Identifier: 
                A5:02:31:28:2E:76:1B:10:11:68:AD:32:5C:8F:DC:00:30:80:BB:7C
    Signature Algorithm: sha256WithRSAEncryption
         ba:0d:dc:9a:f9:12:97:12:b0:7c:d6:07:e7:bd:27:32:46:60:
         75:4b:e3:b4:3e:09:f7:90:53:cd:4d:f5:bf:61:3f:2a:2e:2f:
         d0:c8:50:c2:3b:29:62:10:25:7d:6b:53:48:88:e1:76:60:33:
         52:45:ac:df:5f:49:95:ee:ac:75:81:14:46:2f:e0:26:30:be:
         d8:5d:2b:1c:a2:2f:30:34:c9:f4:9c:e4:c4:86:54:71:69:3d:
         de:2d:97:fe:dc:68:9f:13:d0:b9:86:e8:24:b9:75:04:cf:db:
         1d:cf:d0:36:db:06:b9:87:37:3c:89:25:02:12:8b:fc:42:9e:
         5e:18:69:25:5f:2a:52:ab:5a:a1:19:f6:3f:3b:9c:d3:5d:bd:
         ce:0b:5d:a0:f9:d6:0b:de:05:ff:89:24:b3:ad:9b:4e:5c:9f:
         07:c2:b2:d9:55:44:49:e7:b7:cf:a2:ca:68:ae:64:0d:8a:56:
         43:9b:de:ad:e5:d6:d5:86:76:ba:34:d4:90:e8:0a:ba:26:73:
         8c:4b:7d:8c:92:02:bb:62:2c:9b:83:e8:d3:2f:74:01:72:89:
         b4:a2:08:12:c3:64:90:40:b2:8e:60:fd:db:6b:08:a7:db:32:
         98:f7:7a:ce:c9:78:46:42:7d:09:31:6a:5f:b8:81:87:2f:62:
         1e:e2:d3:7d

Java

这是最简单的

import sun.security.pkcs.PKCS7;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

public class Test {
    public static void main(String[] args) throws CertificateException, IOException {
        FileInputStream fis = new FileInputStream("/Users/wangchen/Desktop/CERT.RSA");
        PKCS7 pkcs7 = new PKCS7(fis);
        X509Certificate publicKey = pkcs7.getCertificates()[0];

        System.out.println("issuer1:" + publicKey.getIssuerDN());
        System.out.println("subject2:" + publicKey.getSubjectDN());
        System.out.println(publicKey.getPublicKey());
    }
}

使用openssl-dev 的C API

#include <openssl/bio.h>
#include <openssl/x509.h>
#include <openssl/pkcs7.h>
#include <string>
#include <iostream>
using namespace std;
string to_string(X509_NAME* name)
{
    BIO* mem = BIO_new(BIO_s_mem());
    if (mem == NULL)
        return NULL;

    if (X509_NAME_print_ex(mem, name, 0, XN_FLAG_RFC2253) < 0)         return NULL;     string str;     char buf[128];     while((BIO_gets(mem, &buf[0], sizeof(buf))) > 0)
    {
        str.append(buf);
    }
    BIO_free(mem);
    return str;
}

int main()
{
    FILE* fp;
    if (!(fp = fopen("CERT.RSA", "rb")))
    {
        fprintf(stderr, "Error reading input pkcs7 file\n" );
        exit(1);
    }
    /* todo: 这里可能有内存漏洞,有空查一下文档 */
    PKCS7* pkcs7 = d2i_PKCS7_fp(fp, NULL);
    X509* cert = sk_X509_pop(pkcs7->d.sign->cert);
    string subject = to_string(X509_get_subject_name(cert));
    string issuer = to_string(X509_get_issuer_name(cert));
    char *modulus = BN_bn2dec(X509_get_pubkey(cert)->pkey.rsa->n);
    cout << subject << endl;
    OPENSSL_free(modulus);
    fclose(fp);
    return 0;
}

 

posted @ 2015-05-06 17:30  demoblog  阅读(6221)  评论(1编辑  收藏  举报